[Lazarus] OOP - where do you start?

[Michael Van Canneyt]

On Fri, 26 Jun 2015, Graeme Geldenhuys wrote:

> Hi,
>
> Last night I was working on a relatively new project. This got me
> thinking... How do others tackle such a task?
>
> So here is my question:
>
>  When faced with a new database related project, where do you start? Do
> you first design the database schema, then build the BOM (Business
> Objects) accordingly? Or, do you first design the BOM, then design the
> database schema to fit.
>
> Personally, most of my project were started by first creating the
> database schema. Don't ask me why, that is just what I did. Maybe it was
> because many of the tools I use, can write much of the boiler plate code
> for me, and they do that by querying a database structure. But I've been
> thinking that with my next project, I'm going to start with the BOM
> first, and see how it goes. I'm assuming the end result should be the
> same, no matter which part I tackled first.
>
> What's your thoughts?

I always start with the data. Almost all applications I ever wrote have databases.
The data structure is in my experience always clear, simple. 
And thus I consider it a good foundation for the rest.

Things start to get messy when you start thinking about functionality.
So that comes next, and the business classes reflect functionality, 
and consequently more susceptible to change.

Luckily the persistence layers I use are flexible enough to allow any mapping between data and business objects,
so the above approach has always worked for me.

I'm tempted to say that working the other way round is bound to lead to confusion.

Michael.